title: Overfeeding over 24 hours does not activate brown adipose tissue in humans.
abstract: BACKGROUND
  Human brown adipose tissue (BAT) is activated with cold exposure, but it is unknown whether overfeeding activates BAT.
  
  
  OBJECTIVE
  We determined BAT activation with cold, fasting, and overfeeding and the relationship of BAT activation with future weight change.
  
  
  METHODS
  Sixteen healthy adults were evaluated during energy balance, fasting, and 24 hours of 200% overfeeding. All subjects had a fluorodeoxyglucose-positron emission tomography (PET) scan after exposure to 16°C to determine cold-induced BAT activity (CIBA). The first six subjects had a second PET scan after 36 hours of fasting to establish the lack of BAT activation at 22°C. The other subjects' second PET scan occurred after 24 hours of overfeeding at 22°C but only if they demonstrated CIBA. Twelve subjects returned at 6 months for reassessment of body composition.
  
  
  METHODS
  BAT was defined in cool scans as voxels with a standardized uptake value (SUV) of 2.0 or greater and Hounsfield units between -250 and -10. Body composition was assessed by dual-energy x-ray absorptiometry.
  
  
  RESULTS
  Although 75% of the subjects demonstrated visible CIBA, none had visual BAT activity after overfeeding. CIBA was greater than that observed in the same defined BAT voxels after fasting (n = 6; 2.9 ± 0.5 vs 1.2 ± 0.2; Δ = -1.7; 95% confidence interval -2.4, -1.0 SUV; P < .01). In the second cohort, CIBA was also higher than observed BAT voxel activity after 24 hours overfeeding (n = 8; 3.5 ± 0.7 vs 0.9 ± 0.2; Δ = -2.6; 95% confidence interval -3.2, -1.9 SUV; P < .01). Baseline CIBA negatively correlated with changes in fat mass after 6 months (r = -0.72, P = .009).
  
  
  CONCLUSIONS
  BAT may be important in weight regulation unrelated to the response to overeating.
authors.affiliation: MD, Obesity and Diabetes Clinical Research Section, National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases, 4212 North 16th Street (Fifth Floor), Phoenix, AZ 85016. mathias.schlogl@nih.gov.
authors.forename: Mathias
authors.initials: M
authors.lastname: Schlögl
authors.forename: Paolo
authors.initials: P
authors.lastname: Piaggi
authors.forename: Pradeep
authors.initials: P
authors.lastname: Thiyyagura
authors.forename: Eric M
authors.initials: EM
authors.lastname: Reiman
authors.forename: Kewei
authors.initials: K
authors.lastname: Chen
authors.forename: Calvin
authors.initials: C
authors.lastname: Lutrin
authors.forename: Jonathan
authors.initials: J
authors.lastname: Krakoff
authors.forename: Marie S
authors.initials: MS
authors.lastname: Thearle
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D050154:Adiposity; D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D003080:Cold Temperature / Q000009:adverse effects; D005215:Fasting; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D005500:Follow-Up Studies; D006801:Humans; D006963:Hyperphagia / Q000503:physiopathology*; D008297:Male; D050177:Overweight / Q000000981:diagnostic imaging / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000378:metabolism; D013997:Time Factors; D015430:Weight Gain
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18